The general goal of our research is to develop models of language comprehension and production which are (a) linguistically adequate and (b) supported by experimental tests of language processings. To this end, we seek to determine how the structural descriptions of sentences (i.e., those specified by formal grammars) relate to the internal (mental) representation(s) of sentences that are computed by listeners in the course of comprehension, and by speakers in the course of production; further, we seek to determine the nature of the information flow that is involved in the construction of such mental representations. This latter effort focuses on an evaluation of the role of three major structural types involved in language processing: lexical, syntactic, and semantic. Thus, for example, we examine in various ways the processes of word recognition, of phrasal and clausal construction, and of sentence interpretation. Research during the first year of grant support has focussed on an experimental evaluation of semantic representation and on the relation of lexical recognition processes to syntactic construction in both recognition and production. Our results on semantic representation (using ratings procedures similar to those of Levelt) indicate no support for the view that surface vocabulary is replaced by definitions at the level of sentence interpretation. Our results on lexical recognition (using lexical decision tasks) indicate the operation of distinct retrieval mechanisms for words from major and minor grammatical categories. Future research will focus on this distinction in sentence contexts.